java - Jtree 和组合框布局

Question

所以我有一个 JTree，它将有不同数量的叶子和节点，我需要在树的叶子旁边添加 JComboBox，但没有树的其他部分。我尝试使用叶子的屏幕位置和边框布局来实现这一点，但盒子总是会关闭，当我有很多叶子时，情况会变得非常糟糕，而且它们似乎也只定位在框架中的 1 个位置，并且随着添加的每个新组合框不断将自己挤压得更薄。我怎样才能实现我想要的目标？

Answer 1

i need to add JComboBoxes next to the leaves of the tree but no other part of the tree

考虑创建您自己的 TreeCellRenderer，将 JComboBox 直接合并到 JTree 中。为了允许编辑 JComboBox，您还需要实现一个 TreeCellEditor 来处理编辑组件以及编辑完成时该组件发生的操作。下面是一个非常简单的示例，它将 JComboBox 放置在 JTree

叶子中的 JLabel 旁边

JFrame frame = new JFrame("Test");
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
DefaultTreeModel model = new DefaultTreeModel(root);
final JTree tree = new JTree(model);

//flyweight pattern components
//editor
final JComboBox editorComboBox = new JComboBox();
final JComboBox viewComboBox = new JComboBox();
final Box box = Box.createHorizontalBox();
final JLabel myLabel = new JLabel();
myLabel.setBorder(BorderFactory.createEmptyBorder(2, 2, 2, 10));
box.add(myLabel);
box.add(Box.createHorizontalGlue());
box.add(viewComboBox);
//Custom Renderer
DefaultTreeCellRenderer renderer = new DefaultTreeCellRenderer (){
    @Override
    public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus) {
        super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);
        if ( leaf ){
            if ( value instanceof MyLeafNode ){
                MyLeafNode node = (MyLeafNode)value;
                viewComboBox.removeAllItems();
                myLabel.setText(value.toString());
                for ( String item : node.items ){
                    viewComboBox.addItem(item);
                }
                viewComboBox.setSelectedItem(node.selected);
                return box;
            }
        }
        return this;
    }
};

//Custom Editor
final DefaultTreeCellEditor editor = new DefaultTreeCellEditor(tree, renderer){

    final ActionListener actionListener = new ActionListener(){
        @Override
        public void actionPerformed(ActionEvent e) {
            cancelCellEditing();
            tree.repaint();
        }
    };

    @Override
    public boolean isCellEditable(EventObject e){
        if ( e.getSource() instanceof JTree ){
            JTree tree = (JTree)e.getSource();
            if ( tree.getLastSelectedPathComponent() == null ){
                return false;
            }
            DefaultMutableTreeNode o = (DefaultMutableTreeNode)tree.getLastSelectedPathComponent();
            return o.isLeaf();
        }
        return false;
    }

    @Override
    public void cancelCellEditing(){
        super.cancelCellEditing();
        DefaultMutableTreeNode node = (DefaultMutableTreeNode)tree.getLastSelectedPathComponent();
        if ( node instanceof MyLeafNode) {
            String sel = editorComboBox.getSelectedItem().toString();
            MyLeafNode mln = (MyLeafNode)node;
            mln.selected = sel;
            editorComboBox.removeActionListener(actionListener);
            tree.repaint();
        }
    }

    @Override
    public Component getTreeCellEditorComponent(JTree tree, Object value, boolean isSelected, boolean expanded, boolean leaf, int row) {
        if ( leaf ){
            if ( tree.getLastSelectedPathComponent() instanceof MyLeafNode ){
                MyLeafNode o = (MyLeafNode)tree.getLastSelectedPathComponent();
                editorComboBox.removeAllItems();
                for ( String item : o.items ){
                    editorComboBox.addItem(item);
                }
                editorComboBox.setSelectedItem(o.selected);
                editorComboBox.addActionListener(actionListener);
            }
            return editorComboBox;

        }
        return super.getTreeCellEditorComponent(tree, value, isSelected, expanded, leaf, row);
    }

};
tree.setCellRenderer(renderer);
TreePath path = new TreePath(new TreeNode[]{root});
tree.expandPath(path);

for ( int i = 0; i < 2; i++ ){
    DefaultMutableTreeNode p = new DefaultMutableTreeNode("P" + i);
    model.insertNodeInto(p, root, i);
    for ( int j = 0; j < 2; j++ ){
        String[] items = {"Item 1", "Item 2", "Item 3", "Item 4"};
        MyLeafNode n = new MyLeafNode("N" + j, items);
        model.insertNodeInto(n, p, j);
    }
    path = new TreePath(new TreeNode[]{root, p});
    tree.expandPath(path);
}
tree.setCellEditor(editor);
tree.setEditable(true);

JScrollPane scroller = new JScrollPane(tree);
frame.add(scroller);
frame.pack();
frame.setVisible(true);

其中MyLeafNode是用于存储JComboBox特定数据的自定义类:

public class MyLeafNode extends DefaultMutableTreeNode{

    private String[] items;
    private String selected;

    public MyLeafNode(String name, String...items){
        super(name);
        this.items = items;
        this.selected = items[0];
    }

}